The present invention relates to a temperature estimating device which estimates temperatures of apparatus constituent members of an electronic apparatus provided with a motor and a temperature estimating method thereof.
In the related art, as an electronic apparatus provided with a motor, for example, an electric power steering device disclosed in JP-A-2002-34283 is proposed. In JP-A-2002-34283, a method of calculating an estimation value of a temperature increase amount of the motor without using a sensor detecting a temperature of the motor is disclosed. Specifically, an estimation value (Δθ) of the temperature increase amount of the motor is calculated on the basis of the following formula (Formula 1). The estimation value (Δθ) of the temperature increase amount calculated as described above is added to a temperature before starting driving the motor, thereby acquiring the temperature estimation value of the motor.
                    Δθ        =                  HTA          ·          TRS          ·                      {                          1              -                              exp                ⁡                                  (                                                            -                      t                                        T                                    )                                                      }                                              Formula        ⁢                                  ⁢        1            
Here, Δθ denotes estimation value of temperature increase amount, HTA denotes power loss of motor driving time, TRS denotes thermal resistance of motor, t denotes driving time of motor, and T denotes thermal time constant of motor.